<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>

        main {
            display: flex;
            justify-content: space-between;
        }

        .aside {
            width: 200px;
            height: 400px;
            background-color: #DD1111;
        }

        .center {
            height: 400px;
            /* 注意：-号两边一定要用空格 */
            width: calc(100% - 200px);
            background-color: chartreuse;
        }
    </style>
</head>
<body>
    <h1>计算宽度（高度）</h1>
    <p>如果现在有一下情景：<br/>左侧的宽度固定为200px，右侧占满余下宽度。<br/>此情况，可以使用css3新特性：计算宽度。</p>
    <main class="main">
        <aside class="aside"></aside>
        <section class="center"></section>
    </main>
</body>
</html>